A diagnosis of irritable bowel syndrome depends largely
on a complete medical history and physical exam.
Criteria for making a diagnosis
Because there are usually no physical signs to definitively diagnose irritable
bowel syndrome, diagnosis is often a process of elimination. To help in
this process, researchers have developed diagnostic criteria, known as
Rome criteria, for IBS and other functional gastrointestinal disorders
— conditions in which the bowel appears normal but doesn't function
normally.
According to these criteria, you must have certain signs and symptoms
before a doctor diagnoses irritable bowel syndrome. The most important
are abdominal pain and discomfort lasting at least 12 weeks, though the
weeks don't have to occur consecutively. You also need to have at least
two of the following:
- A change in the frequency or consistency of your stool. For example,
you may change from having one normal, formed stool every day to three
or more loose stools daily. Or you may have only one hard stool every
three to four days.
- Straining, urgency or a feeling that you can't empty your bowels
completely.
- Mucus in your stool.
- Bloating or abdominal distension.
Your doctor will likely assess how you fit these criteria, as well as
whether you have any other signs or symptoms that might suggest another,
more serious condition. Some red flag signs and symptoms that might prompt
your doctor to do additional testing include:
- New onset after age 50
- Weight loss
- Fever
- Recurrent vomiting
If you have these or other red flag signs or symptoms, you'll need additional
testing to further assess your condition.
If you fit the IBS criteria and don't have any red flag signs or symptoms,
your doctor may suggest a course of treatment without doing additional
testing. But if you don't respond to that treatment, you will likely require
more tests.
Additional tests
Your doctor may recommend several tests, including stool studies to check
for infection or malabsorption problems. Among the tests that you may
undergo to rule out other causes for your symptoms are the following:
- Flexible sigmoidoscopy. This test examines the lower part of the
colon (sigmoid) with a flexible, lighted tube (sigmoidoscope).
- Colonoscopy. In some cases, your doctor may perform this diagnostic
test, in which a small, flexible tube is used to examine the entire
length of the colon.
- Computerized tomography (CT) scan. CT scans produce cross-sectional
X-ray images of internal organs. CT scans of your abdomen and pelvis
may help your doctor rule out other causes of your symptoms.
- Lactose intolerance tests. Lactase is an enzyme you need to digest
the sugar found in dairy products. If you don’t produce this
enzyme, you may have problems similar to those caused by irritable
bowel syndrome, including abdominal pain, gas and diarrhea. To find
out if this is the cause of your symptoms, your doctor may order a
breath test or ask you to exclude milk and milk products from your
diet for several weeks.
- Blood tests. Celiac disease (nontropical sprue) is sensitivity
to wheat protein that also may cause signs and symptoms like those
of irritable bowel syndrome. Blood tests may help rule out that disorder.
Complications
Diarrhea and constipation, both signs of irritable bowel syndrome, can
aggravate hemorrhoids. In addition, irritable bowel syndrome can interfere
with your work, your relationships with friends and family, and your ability
to live your life to the fullest. At times, you may feel discouraged or
depressed. If you avoid certain foods, you also may not get enough of
the nutrients you need, leading to malnourishment.
Treatment
Because it's not clear what causes irritable bowel syndrome, treatment
focuses on the relief of symptoms so that you can live your life as normally
as possible.
In most cases, you can successfully control mild signs and symptoms of
irritable bowel syndrome by learning to manage stress and making changes
in your diet and lifestyle. But if your problems are moderate or severe,
you may need more than lifestyle changes alone can offer. Your doctor
may suggest
- Fiber supplements. Taking fiber supplements such as psyllium (Metamucil)
or methylcellulose (Citrucel) with fluids may help control constipation.
- Anti-diarrheal medications. Over-the-counter medications such as
loperamide (Imodium) can help control diarrhea.
- Eliminating high-gas foods. If you have bothersome bloating or
are passing significant amounts of gas, your doctor may also ask you
to cut out such items as carbonated beverages, salads, raw fruits
and vegetables, cabbage, broccoli and cauliflower.
- Anticholinergic medications. Some people need medications that
affect certain activities of the nervous system (anticholinergics)
to relieve painful bowel spasms.
- Antidepressant medications. If your symptoms include pain or depression,
your doctor may recommend a tricyclic antidepressant or a selective
serotonin reuptake inhibitor (SSRI). These medications help relieve
depression as well as inhibit the activity of neurons that control
the intestines. For diarrhea and abdominal pain, your doctor may suggest
tricyclic antidepressants, such as imipramine (Tofranil) and amitriptyline.
Side effects of these drugs include drowsiness and constipation. SSRIs
such as fluoxetine (Prozac, Sarafem) or paroxetine (Paxil) may be
helpful if you're depressed and have pain and constipation.
- Counseling. If antidepressant medications don't work, you may have
better results from counseling if stress tends to worsen your symptoms.
Some research has shown that some people with IBS might benefit from antibiotic
treatment, but this remains unproved.
Medication specifically for IBS
Alosetron (Lotronex) is currently the only drug available to treat IBS.
Alosetron is a nerve receptor antagonist that's supposed to relax the
colon and slow the movement of waste through the lower bowel. But the
drug was removed from the market just nine months after its approval when
it was linked to at least two deaths and severe side effects in 113 people.
In June 2002, the Food and Drug Administration decided to allow alosetron
to be sold again — with restrictions. The drug can be prescribed
only by doctors enrolled in a special program and is intended for severe
cases of diarrhea-predominant IBS in women who haven't responded to other
treatments. Alosetron is not approved for use by men.
Generally, alosetron should only be used if usual therapy for IBS has
failed. Additionally, it should only be prescribed by a gastroenterologist
with expertise in IBS because of the potential side effects.
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